Re: [PATCH 0/4] allow multiple kthreadd's

Tejun Heo
2020-05-05T21:10:02Z

Hello,

On Tue, May 05, 2020 at 05:01:18PM -0400, J. Bruce Fields wrote:
> On Mon, May 04, 2020 at 10:15:14PM -0400, J. Bruce Fields wrote:
> > Though now I'm feeling greedy: it would be nice to have both some kind
> > of global flag, *and* keep kthread->data pointing to svc_rqst (as that
> > would give me a simpler and quicker way to figure out which client is
> > conflicting). Could I take a flag bit in kthread->flags, maybe?
>
> Would something like this be too hacky?:

It's not the end of the world but a bit hacky. I wonder whether something
like the following would work better for identifying worker type so that you
can do sth like

if (kthread_fn(current) == nfsd)
return kthread_data(current);
else
return NULL;

Thanks.

diff --git a/kernel/kthread.c b/kernel/kthread.c
index bfbfa481be3a..4f3ab9f2c994 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -46,6 +46,7 @@ struct kthread_create_info
struct kthread {
unsigned long flags;
unsigned int cpu;
+ int (*threadfn)(void *);
void *data;
struct completion parked;
struct completion exited;
@@ -152,6 +153,13 @@ bool kthread_freezable_should_stop(bool *was_frozen)
}
EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);

+void *kthread_fn(struct task_struct *task)
+{
+ if (task->flags & PF_KTHREAD)
+ return to_kthread(task)->threadfn;
+ return NULL;
+}
+
/**
* kthread_data - return data value specified on kthread creation
* @task: kthread task in question
@@ -244,6 +252,7 @@ static int kthread(void *_create)
do_exit(-ENOMEM);
}

+ self->threadfn = threadfn;
self->data = data;
init_completion(&self->exited);
init_completion(&self->parked);

--
tejun